One proposed cooling device drives an electric oil pump to supply a flow of oil as a driving source of a transmission to a radiator and cool down the oil flow when the temperature of the oil flow reaches or exceeds a preset temperature level (see, for example, Japanese Patent Laid-Open Gazette No. 2000-227150). In this prior art structure, the motor is arranged extremely near to a torque converter located with the transmission in one identical housing. Cooling the oil flow accordingly prevents a temperature rise of the motor.